Apparatus for automatically producing mold parts

ABSTRACT

In an automatic mold part producing apparatus having a mold chamber which is filled with mold forming material that subsequently is compressed between a pair of opposite end walls, or pattern boards the mold forming material is forced into said mold chamber by means of pressurized air, the pressure of which is gradually or stepwise increased during the chamber filling operation, for the purpose of achieving uniform compactness or density of the mold forming material throughout the height of the mold chamber.

Elite States atent Gunnergaard [4 1 Apr. 29, 1975 APPARATUS FORAUTOMATICALLY PRODUCING MOLD PARTS [75] Inventor: Marius Gunnergaard.Lyngby Denmark [73] Assignee: Dansk lndustri Syndikat A/S,

Herle\' Denmark [22] Filed: Sept. 19. I972 [21] Appl. No.: 290.369

[30] Foreign Application Priority Data Sept. 23. 1971 Denmark 4651/71[52] US. Cl. 164/200; 141/67; 164/40 [51} Int. Cl. B22c 15/28 [581 Fieldof Search 164/19. 20. 21, 22, 37. 164/40. 200.155. 201, 202: 141/67. 68

[56] References Cited UNITED STATES PATENTS 3.274.651 9/1966 Oliveira164/22 FOREIGN PATENTS OR APPLICATIONS 603.754 8/1960 Canada 164/40Primary Examiner- Francis S. Husar Assistant E.\'aminer.lohn E. ROethelAltorney, Agent, or Firm-Imirie, Smiley & Linn In an automatic mold partproducing apparatus having a mold chamber which is filled with moldforming material that subsequently is compressed between a pair ofopposite end walls or pattern boards, the mold forming material isforced into said mold chamber by means of pressurizedair, the pressureof which is gradually or stepwise increased during the chamber fillingoperation, for the purpose of achieving uniform compactness or densityof the mold forming material throughout the height of the mold chamber.

ABSTRACT 4 Claims, 4 Drawing Figures APPARATUS FOR AUTOMATICALLYPRODUCING MOLD PARTS BACKGROL'ND OF THE INVENTION This invention relatesto a method of operating automatic mold part producing apparatuscomprising a pressing chamber which. on one side. is closed by apressure plate or pattern board that reciprocally is displaceable in theaxial direction and. on the other side, by a counterpressure plate orpattern board which. for preference. remains stationary during thepressing operation. Through one or more passage apertures the chambercommunicates with a supply bin for sand or similar mold forming materialwhich is forced into and fills the mold chamber and subsequently iscompressed by the movement of the pressure plate towards thecounterpressure plate.

A machine of this type for automatically producing mold parts isdisclosed by Jeppesen US Pat. No. 3.008.199. In practice. the moldchamber of this machine is. in its top and/or side walls, provided withone or more slots through which the sand from the supply bin is forcedinto the mold chamber. for instance, by means of centrifugal impellersor by the use of pressurized air.

When pressurized air is used for this purpose, the supply bin, afterhaving received the requisite quantity of sand. is hermetically sealedoff from the surroundings. Following this. the upper part of the supplybin is connected to a pressurized air tank so that the air pressure willforce the sand into the mold chamber until it is filled.

When using the prior art apparatus it has been found that thecompactness or density of the sand in the filled mold chamber decreasesin the vertical direction and that this variation of the compactnesschanges only negligibly in the course of the subsequent pressingoperation. This is connected with the circumstance that the sandpossesses a very low degree of flow. The varying compactness of the sandhas the effect that the pressure plate which. normally, rests on thebottom of the chamber. tends to rise slightly therefrom during thecompressing movement whereby the precision of the mold parts produced isadversely affected. Moreover, by the termination of the compressingmovement, portions or fractions of the mold part formed may be torn offas the pressing plate, during this phase. will again sink down intoabutment against the bottom of the mold chamber.

In addition, the varying compactness of the sand results in a varyingresilience in the mold part when relieved from pressure by the backwardmotion of the pressure plate. As a consequence thereof. thepressurerelieved mold part will have a slightly greater thickness at thebottom than at the top and. when assembling a series of such mold partsso as to form a coherent string of molds. it will not in allcircumstances be possible to ensure the desired tightness at the contactfaces between the individual mold parts.

SUMMARY OF THE INVENTION The disadvantages enumerated above can beremedied by the method according to the invention the concept of whichresides in increasing the speed at which the material particles areforced into the mold chamber during the chamber filling operation.

The increase of the particle velocity during the filling operation. incorrelation with the very low degree of flow of the mold part material,results in a practically uniform material compactness in the verticaldirection of the mold chamber, which is due to the circumstance that,during the filling of the chamber. the adverse effect of thegravitational force on the compactness of the material is compensated bythe increase of particle velocity.

When. in a known manner, pressurized air is utilized to force the moldpart material into the mold chamber, the air pressure above the volumeof material present in the supply bin may be increased while the moldchamber is being filled. In this way it becomes possible, while usingrelatively simple means, to achieve the desired variation in theparticle velocity during the filling of the chamber.

The invention also relates to an apparatus intended for carrying out thenew method explained above. This apparatus comprises a supply bin whichis connected with either at least one pressurized air tank via at leasttwo valves that can be successively opened, or with at least twoseparate pressurized air tanks via individual valves that can besuccessively opened. or with at least one pressurized air tank via anadjustable valve which is controlled in such a way that its flow areaincreases while the mold chamber is being filled.

Each of the alternative embodiments is easy to realize in practice andeach renders the desired increase in the air pressure possible duringthe filling of the mold chamber, if so required, in an automatic orsemiautomatic manner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectionalview through the relevant components of an embodiment of the apparatus.and

FIGS. 2, 3 and 4 are diagrammatic plan views of the apparatus in threedifferent embodiments.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a mold chamber C havingside walls 1, a bottom 2 and a top wall 3, as well as two end walls thatare constituted by a counterpressure plate 4 and a pressing plate or ram5, respectively. These two end walls 4 and 5 each carry a pattern plate6 and a model part 7.

Through a slot 8 in the top wall 3, the mold chamber C can receive sandor similar mold part material from a hopper-like supply bin 9 that isassumed to be filled with sand up to the level 10 shown in broken lines.

In the situation shown, supply bin 9 is sealed off from the surroundingsbut, via one or more ducts 11 with a valve 12, it communicates with oneor more pressurized air tanks 13.

According to FIG. 2, the apparatus is provided with two pressurized airtanks 13 which through individual ducts 11a and 11b with associatedvalves 12a and 12b are connected to supply bin 9. At the start of thefilling operation, only valve 12a is assumed to be open and,furthermore. the two pressurized air tanks 13 are assumed to have auniform starting pressure. When the mold chamber C has been partiallyfilled, valve 12b is also opened, whereby it is possible to achieve apressure increase above the sand in supply bin 9, such pressure increaserequiring an increasing supply of air per unit of time inasmuch as thevolume above the sand in creases gradually as mold chamber C is beingfilled.

Other possibilities for operating the apparatus illustrated in FIG. 2consist in allowing the two pressurized air tanks 13 to have differentstarting pressure and. possibly, different capacities, and the valves12a and 12b maythen be operative alternatively so that only one of thesevalves is open at a time. The flow capacity of the valves can beadjusted at will,

Also according to FIG, 3 the supply bin 9 is connected with two ducts11a and 11b with valves 12a and 12b, but these ducts communicate with acommon pressurized air tank 13. The operation can proceed as explainedin connection with FIG. 2.

According to FIG. 4 the supply bin 9 communicates with a singlepressurized air tank 13 via a single duct 11 fitted with an adjustablevalve 120. It is possible for this valve to be controlled according to apredetermined program with a view to changing the flow area, or else itmay be controlled dependently upon the pressure actually prevailinginside supply bin 9 and pressurized air tank 13 in a way so as toachieve the desired filling process of'mold chamber C.

I claim:

1. Apparatus for' automatically producing mold parts, comprising ahorizontally disposed mold chamber naving a pair of opposite, end wallsof which at least one is axially displaceable, a mold material supplybin above said chamber, at least one passage opening means formingcommunication between the top of said mold chamber and the bottom ofsaid supply bin for vertically supplying material from said bin to saidchamber, and at least one pressurized air tank communicating with saidsupply bin above the normal level of material therein throughvalve-means for supplying air acting on said supplied material in twosuccessively increasing pressure stages during the chamber fillingoperation.

2. Apparatus according to claim 2 wherein said valve means comprises atleast one adjustable valve having a flow area that is increased duringthe chamber filling operation.

3. Apparatus according to claim 2 comprises at least two pressurized airtanks communicating with said supply bin through individual andsuccessively operated valves.

4. Apparatus according to claim 1 wherein said valve means comprises twosuccessively operated valves.

1. Apparatus for automatically producing mold parts, comprising ahorizontally disposed mold chamber having a pair of opposite end wallsof which at least one is axially displaceable, a mold material supplybin above said chamber, at least one passage opening means formingcommunication between the top of said mold chamber and the bottom ofsaid supply bin for vertically supplying material from said bin to saidchamber, and at least one pressurized air tank communicating with saidsupply bin above the normal level of material therein through valvemeans for supplying air acting on said supplied material in twosuccessively increasing pressure stages during the chamber fillingoperation.
 2. Apparatus according to claim 2 wherein said valve meanscomprises at least one adjustable valve having a flow area that isincreased during the chamber filling operation.
 3. Apparatus accordingto claim 2 comprises at least two pressurized air tanks communicatingwith said supply bin through individual and successively operatedvalves.
 4. Apparatus according to claim 1 wherein said valve meanscomprises two successively operated valves.